1. Technical Field of the Invention
The present invention relates to a radio frequency circuit module, such as monolithic radio frequency integrated circuit module or a hybrid microwave integrated circuit module, formed by mounting circuit elements on a circuit substrate having dielectric layers for a module and a communication apparatus using the radio frequency circuit.
2. Description of the Prior Art
Heretofore, there is a radio frequency integrated circuit module having a multi-layer circuit substrate, on which circuit elements such as active elements including transistors and diodes and passive elements including resistors and inductors, and wiring for mutually connecting the circuit elements are mounted. When radio frequency integrated circuit module are mutually connected, a transmission path having a high shield property, such as a coaxial line, is used between transmission and reception terminals in many cases.
FIG. 16A is an oblique view conceptually showing the vicinities of transmission and reception terminals of a conventional radio frequency integrated circuit module. FIG. 16 B is a sectional view of FIG. 16A in a coaxial line direction. FIG. 16B shows a radio frequency integrated circuit module having a multi-layer circuit substrate 2001 formed by interposing an inner conductor 2002 having circuit elements mounted thereon, between first and second grounds 2003 and 2004 to form a strip line 2005.
The inner conductor 2002 is led to a pad 2007 through a via (through hole) 2006. The pad 2007 is a transmission and reception terminal having a fixed area provided on a top layer or a bottom layer. A central conductor 2009 of a coaxial line 2008 is fixed to the pad 2007 by adhering using solder 2010. Furthermore, the first and second grounds 2003 and 2004 are electrically connected through vias 2011. An outer conductor 2012 of the coaxial line 2008 is adhered and fixed to the first ground 2003 by solder 2013.
Radio frequency signals can be inputted to and outputted from the radio frequency integrated circuit module of such construction in such a state that circuit elements are integrated therein.
In the conventional radio frequency integrated circuit module, however, the central conductor of the coaxial line to be shielded around it is exposed at a portion connected to the pad. Therefore, the central conductor is susceptible to electromagnetic waves radiated from circuit elements and wiring mounted near the central conductor or external electromagnetic noise.
Furthermore, in some cases, for example, the central conductor of the coaxial line is pulled from the outside and consequently a warp is caused in the multi-layer circuit substrate, or stress from a contained cabinet is applied to the coaxial line. Sometimes in this case, solder peels from the pad or ground, or a metal pattern peels from the multi-layer circuit substrate, and resultant wire breaking or poor connection degrades the electric connection state.
Furthermore, there is a disadvantage that an unnecessary inductance component increases because the via is provided to connect the inner conductor, and consequently the radio frequency characteristics are degraded. Furthermore, since the central conductor of the axial line is not connected to the inner conductor in a three-dimensional rectilinear way, the electromagnetic field near the via is disturbed and the transmission characteristics of the radio frequency signal are degraded in some cases.
A problem of the present invention is to provide a radio frequency integrated circuit that is not susceptible to the influence of the electromagnetic waves and that is not degraded in electrical connection state, and a radio frequency integrated circuit module and a communication apparatus having the radio frequency integrated circuit mounted thereon.
In order to solve the above described problem, the present invention is a radio frequency circuit including circuit elements mounted on a multi-layer circuit substrate having a dielectric, characterized in that an exposed connection portion is provided by removing a part of the dielectric, and a conductor line connected to the circuit elements and a transmission path for transmitting a radio frequency signal from/to the conductor line are connected together in a bottom portion of the exposed connection portion so as to be rectilinear in a three dimensional way.
To be concrete, the exposed connection portion is disposed in such a position as to be less susceptible to influence of electromagnetic waves from the circuit elements. Furthermore, preferably, a connection portion of the conductor line and the transmission path is covered by a conductor having such a hole as to be able to take out the transmission path. In addition, the conductor line is formed in a taper form toward the connection portion of the conductor line and the transmission path. Furthermore, ceramic or alumina can be used as the dielectric.
Furthermore, to be concrete, the conductor line and the transmission path are connected together so as to be rectilinear in a three dimensional way by providing a step in the bottom portion of the exposed connection portion. Furthermore, a part of the bottom portion of the exposed connection portion is a surface of ground, and an outer conductor of the transmission path is electrically connected to the ground. Furthermore, characteristic impedance matching in the connection portion can also be accomplished by changing the distance between the conductor and the connection portion of the conductor line and the transmission path or by changing the thickness of a dielectric of the multi-layer circuit substrate disposed across the connection portion of the conductor line and the transmission path from the exposed connection portion.
Furthermore, the present invention is a module including a radio frequency circuit, the radio frequency circuit including circuit elements mounted on a multi-layer circuit substrate having a dielectric, characterized in that in the radio frequency circuit, an exposed connection portion is provided by removing a part of the dielectric, and a conductor line connected to the circuit elements and a transmission path for transmitting a radio frequency signal to the conductor line are connected together in a bottom portion of the exposed connection portion so as to be rectilinear in a three dimensional way.
Furthermore, a communication apparatus of the present invention is characterized in that the module is mounted on a radio frequency signal processor.
Furthermore, in the radio frequency circuit of the present invention, a multi-layer circuit substrate is formed of at least three layers including first to Nth (Nxe2x89xa73) layers. Such a strip line that an inner conductor disposed in some inner layer is interposed between first and second grounds has an exposed connection portion in its end portion. The exposed connection portion is formed by removing a dielectric layer or a metal layer on an upper side or a lower side of the inner conductor. A central conductor of a coaxial line serving as a transmission path is connected to the inner conductor exposed in the bottom portion of the exposed connection portion so as to be rectilinear. The characteristic impedance of the strip line is made equal to that of the coaxial line.
According to the present invention, the transmission characteristic of the connection portion between the inner conductor in the multi-layer circuit substrate and the coaxial line can be improved, and highly reliable signal transmission with a reduced reflection loss and radiation loss can be conducted. Furthermore, the shield performance in the connection portion between the inner conductor and the coaxial line can be improved. It is possible to suppress the interference of electromagnetic noise in the surroundings and conduct highly reliable signal transmission without radiating unnecessary electromagnetic waves to the surroundings.
Furthermore, the mechanical strength in the connection portion between the inner conductor in the multi-layer circuit substrate and the coaxial line can be enhanced. It is possible to prevent wire breaking or poor connection caused by deformation of the connection portion or signal degradation caused thereby. Highly reliable signal transmission can be conducted.